1.3. EVMS terminology

To avoid confusion with other terms that describe volume
management in general, EVMS uses a specific set of terms.
These terms are listed, from most fundamental to most comprehensive,
as follows:

Logical disk

Representation of anything EVMS can access as a physical disk.
In EVMS, physical disks are logical disks.

Sector

The lowest level of addressability on a block
device. This definition is in keeping with the standard
meaning found in other management systems.

Disk segment

An ordered set of physically contiguous
sectors residing on the same storage object.
The general analogy for a segment is to a traditional disk
partition, such as DOS or OS/2 ®

Storage region

An ordered set of logically contiguous sectors
that are not necessarily physically contiguous.

Storage object

Any persistent memory structure in EVMS that can be used to
build objects or create a volume. Storage object is a generic term for disks, segments, regions, and feature objects.

Storage container

A collection of storage objects. A storage
container consumes one set of storage objects and produces new
storage objects. One common subset of storage containers is volume groups,
such as AIX® or LVM.

Storage containers can be either of type private or cluster.

Cluster storage container

Specialized storage containers that consume only disk objects
that are physically accessible from all nodes of a cluster.

Private storage container

A collection of disks that are physically accessible from all
nodes of a cluster, managed as a single pool of storage, and owned and accessed
by a single node of the cluster at any given time.

Shared storage container

A collection of disks that are physically accessible from all
nodes of a cluster, managed as a single pool of storage, and owned and accessed
by all nodes of the cluster simultaneously.

Deported storage container

A shared cluster container that is not owned by any node of the cluster.

Feature object

A storage object that contains an EVMS native feature.

An EVMS Native Feature is a function of volume management designed
and implemented by
EVMS. These features are not intended to be backward compatible with other
volume management technologies.

Logical volume

A volume that consumes a storage object and exports
something mountable. There are two varieties of logical volumes: EVMS Volumes
and Compatibility volumes.

EVMS Volumes contain EVMS native metadata and can support all
EVMS features. /dev/evms/my_volume would be an example
of an EVMS Volume.

Compatibility volumes do not contain any EVMS native metadata.
Compatibility volumes are backward compatible to their particular scheme, but
they cannot support EVMS features. /dev/evms/md/md0 would
be an example of a compatibility volume.